Making Synths out of Audio Cassettes

8bit Mixtapes are simple Arduino-based sound and beat generators based on ATtiny 84s and 85s and designed fit inside old audio cassettes, or at least be about that size. Founded by [Dusjagr], [Ucok] and [Lyok], and including participants from around the globe, 8bit Mixtapes are small synthesizers that play one-line algorithmic symphonies, simple sound generators that work off of a single line of code.

The project has been going on for a number of years, with several different iterations released over the years–the most recent is the Mixtape NEO, released about a month ago that features audio bootloading and a row of NeoPixel LEDs. It’s well documented and fully open source, with a code repository and wiki. The arty PCBs look great as well!

8bit Mixtapes are a natural project for electronics students to tackle. An ATtiny85 with two pots and two buttons? Pretty simple, and the musical payoff makes it a cinch for one-day workshops. The code simplicity makes it easy to modify the software as well.

Quirky synths are Hackaday’s bag, including one we published previously that controls a hexagonal matrix of LEDs.

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The Smart Pen

“Ugh. You mean I have to press down on the pen’s button to open it? Gross.” In this day-and-age when we can swipe on our phones and do voice recognition, there seems no reason we should have to press a button. How antiquated. So [Marek Baczynski] modernized his pen for swiping and voice control. It’s also sure to get all the kids back to working on their penmanship.

Seriously though, not all hacks have to be serious. [Marek] and [Ghlargh] added a servo to activate the button, and then [Marek] added Bluetooth to control the servo. After writing a phone app, he was able to swipe down to open it and down again to close it. Then, after some prompting from Redditers he added voice control from his laptop. We think he could have done a more professional job with the way he attached the pen to the laptop, perhaps he could have 3D printed something instead of just using tape, or maybe made something using CNC or a laser cutter. An important hack such as this deserves as much. Now he need only say “Computer. Open pen.” and the tedious task is taken care of. Seeing is believing so check it out in the video below.

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Ambitious ATtiny85 Board Tests a Beginner’s Skills

[Chris O’Riley] has been playing around with Arduinos for around a year, and decided he wanted a breadboardable ATtiny85 in order to prototype using the actual controller that would be used in the final project. He wants to use it to interface with a Bosch BMP280 pressure sensor, but for now it stands alone.

It’s a simple board with the Tiny85, 3.3 V and 5 V regulators, a power LED, as well as the usual resistors and caps [Ed: not resistor sand caps]. The double-sided PCB [Chris] milled himself — he’s an illustrator and photographer by day, so it’s no surprise the board turned out gorgeous. He designed the board in Illustrator after taking a stab at Eagle, then ran it through his CNC to mill the circuits using a .017 inch end mill as well as drilling the vias. He add solder paste using the tip of a knife, but after messing around with an iron, he ended up investing in a hot air rework station.

We love our Tiny85s here on Hackaday. Check out the ATtiny85 gaming console, the NTSC-generating ATTiny85, and making DIY I2C devices with the chip.

Single Part Boost Converter Challenge (Completed)

[Josh] posed an interesting challenge. Create a boost converter that can light a blue LED using a nearly dead battery and one part. Well, we were skeptical until we saw he wasn’t counting an ATtiny processor as a part. You can see a video of the challenge, below.

The challenge has already been solved, so if you view the link, you might want to avoid the comments until you’ve had time to think about your own solution. We’ll confess, the first one we thought of was probably not workable for reasons [Josh] explains. The final answer neatly fits the criteria of a hack.

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Copper Foil Makes Music–With a Little Help

Craft stores are often the source of odd inspiration. In the stained glass section, we’ve seen the copper foil, and even used it to prototype some RF circuits on the tops of shoeboxes. However, we could never get a good method for connecting ICs to the relatively thick foil. [Bryan Cera] did it though. His paperSynth uses some paper and cardboard for a substrate, copper foil, and an ATtiny CPU to make music. You can see the device in operation in the video, below.

The copper foil is sticky and it isn’t conductive on the back, so anywhere the foil is supposed to touch, you need a blob of solder. We wouldn’t trust the insulation by itself to cross wires, but with a bit of insulating material between–a piece of paper or electrical tape, for example–you could probably cross with impunity. For an RF circuit, you might even make low-value capacitors like that.

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A LED Strip Clock As Linear As Time

We love custom clocks here at Hackaday, and are always thrilled to see each inventive means of time-keeping. In a seldom-seen take on the familiar device, the [Bastel Brothers]’s LED Strip Clock’s sleek profile finds itself in good company.

The clock is a two-metre strip of 60 LEDs; every minute past the current hour corresponds to one lit LED, every fifth LED is turned to red in order to make reading minutes easier. So 3 red LEDs +3 green LEDs=18 minutes, with the hour marked by a third color. Sounds complex, but the [Brothers] are quick to say you get used to it quickly, especially when the 6 o’clock LED is centered at some noticeable object or feature.

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Saturday Clock: An 0.000011574Hz ATtiny85 clock

In these times when we try to squeeze out extra clock cycles by adding more cores to our CPUs and by enlisting the aid of GPUs, [Ido Gendel] thought it would be fun to go in the exact opposite direction, supply a clock to the ATtiny85 that cycles only once per day, or at 0.000011574Hz. What application could this have? Well, if he could do it in seven instructions or less, how about turning on an LED at sunset Friday evening, to indicate the start of the Jewish Shabbat (Saturday), and turn it off again at sunset Saturday evening.

Notice the subtlety. A clock that cycles once per day means you can execute at most one instruction per day. Luckily on AVR microcontrollers, the instructions he needed can execute in just one cycle. That of course meant diving down into assembly code. [Ido] wasn’t an assembly wizard, so to find the instructions, he compiled C code and examined the resulting assembly until he found what he needed. One instruction turns on the LED and the instruction immediately following turns it off again, which normally would make it happen too fast for the human eye to register. But the instruction to turn it on runs on Friday evening and the very next instruction, the one that turns it off, doesn’t run until Saturday evening. Do you feel like you’re in a science fiction story watching time slowed down? Freaky. A few NOPs and the jump for the loop take up the remaining five cycles for the week.

For the source of the clock he chose to use an LDR to detect when the light level dropped at the end of the day. The problem he immediately ran into was that clouds, bird shadows, and so on, also cause drops in the light level. The solution he found was to widen the light and dark range by adding a TLV3702 push-pull output comparator and some resistors. [Ido] gives a detailed explanation of the circuit in the video after the break.

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